The present invention relates generally to improvements in or relating to the so-called "vent type extruder" or more particularly to an improved multi-vents type extruding machine employable to mold any desired shape of articles by extruding a kind or kinds of synthetic resin materials mixed or not mixed with other raw material through the machine.
Most of the aforesaid resin materials and other raw material unexceptionally contain a considerable amount of moisture and gas therein and when they are forced into an extruder to form any desired shape of articles, the questioned amount needs to be given vent from the materials under heating and constrictively extruding treatments. The result is that bubbles are sporadically caused in the inside of thus molded articles, giving rise to inferior quality of the latter.
It is therefore customary with the plastics industry that all the raw materials to be treated for the purpose should be completely dried up prior to the heating and extruding treatments thereby to give vent to the moisture and gas co ntained therein.
In order to save an extra time for the above-mentioned drying treatment, some of the existing extruders are designed to operate without appealing to the desiccating treatment; according to which there is formed a single ventage in open-mouthed relation adjacent to an extruding mouth of a heating cylinder wherein a quantity of moisture and gas contained in completely molten raw materials can be fully discharged.
However, in the initial melting stage, the raw materials are not in a state of giving vent to the moisture and gas contained therein, thus necessitating repetition of extruding operations until the complete venting result can be attained.
Further according to the above-mentioned conventional vent type extruders, an inlet for putting raw materials through is formed into a structurally much simplified single one opening provided with a hopper means through which a variety of resin materials mixed or not mixed with other material must be concentratively put so that when these materials, soft or hard in quality, are promiscuously cast into the hopper means, there is inevitably caused a great difference in melting speed between these qualities, thereby making it practically quite infeasible to obtain fusible mixture of the materials that can be completely mixed or kneaded in a uniforly molten state. Thus there still remains the disadvantage that no high quality articles can be molded through extrusion.